Nd and yb containing phosphate glasses for laser use

ABSTRACT

1. A GLASS FOR LASER USE COMPRISING THE FOLLOWING COMPONENTS, IN PRESENT BY WEIGHT-40-90% OF METAPHOSPHATES SELECTED FROM THE GROUP CONSISTING OF LI, NA, K, ZN, CD, BA, PB, MG, CA, AND SR, 5-50% OF PHOSPHATES OF ELEMENTS SELECTED FROM THE GROUP CONSISTING OF AL, ZR, B, AND CE, 1-7% OF TRIVALENT NEODYMIUM ND3+, AND 0.3-5% OF TRIVALENT YTTERBIUM UB3+, SAID GLASS HAVING A THERMAL EXPANSION COEFFICIENT IN THE RANGE OF 50-160X10**-7 1/DEGREE, A MICROHARDNESS IN THE RANGE OF 300-450 KG./MM,2,A QUANTUM EFFICIENCY OF TRANSMISSION OF ND3+&gt;YB3+HIGHER THAN 0.7, THE SECTION OF STIMULATED EMISSION OF YTTERBIUM AT X=1060 NM. BEING EQUAL TO ABOUT 2.5-5X10**-21 CM.2, AND A MAXIMUM INVERSION AT ELECTRIC ENERGY OF PUMPING OF 80 JOULES/CM.3 IS 1.5 TO 2X10**19 1/CM.2.

1974 l. M. BUZHINSKY EIAL 5,

Nd AND Yflr CONTAINING PHOSPHATE GLASSES FQR LASER USE Filed Sept. 18, 1972 1 J Z 5/77 4 U n o c I I I Z 5 7,5 m j United States Patent 3,846,142 Nd AND Yb CONTAINING PHOSPHATE GLASSES FOR LASER USE Igor Mikhailovich Buzhinsky, Pervomaiskaya ulitsa 5,

kv. 46, Lytkarino Moskovskoi oblasti, U.S.S.R.; Valentin Pavlovich Gapontsev, ulitsa Godovikova 1, kv. 110; and Mark Efremovich Zhabotinsky, Pogodinskaya ulitsa 2/3, kv. 53, both of Moscow, U.S.S.R.; Anatoly Andreevich Izyneev, Vokzalnaya ulitsa 19, kv. 18, Fryazino Moskovskoi oblasti, U.S.S.R.; Elizaveta Ivanovna Koryagina, Oktyabraskaya ulitsa 15, kv. 31, Lytharino Moskovskoi oblasti, U.S.S.R.; Valery Borisovich Kravchenko, ulitsa Lenina 14, kv. 47, Fryazino Moskovskoi oblasti, U.S.S.R.; Jury Petrovich Rudnitslq', ulitsa Ostrovityanova 31, kv. 298; Evgeny Ivanovich Sverchkov, ulitsa Butyrsky val 32, kv. 61; and Nikolai Efimovich Alexeev, ulitsa Gorkogo 8, korpus 1, kv. 21, all of Moscow, U.S.S.R.; and Boris Leonidovich Davydov, ulitsa Nakhimova 17, kv. 63, Fryazino Moskovskoi Oblasti, U.S.S.R. No Drawing. Filed Sept. 18, 1972, Ser. No. 290,146

Int. Cl. C03c 3/16, 3/30; C091; 1/36 US. Cl. 106-47 R 8 Claims ABSTRACT OF THE DISCLOSURE Phosphate base glass used in laser apparatus generating and amplifying high-energy light monopulses having a duration of less than 10- sec. on )v=l060 nm. The glass containing metaphosphates of the elements Li and/ or Na, and/or K, and/or Mg, and/0r Ca, and/or Sr, and/or Cd, and/or Ba, and/or Pb, in the amount of 40 90%, phosphates of elements Al and/or Zr, and/or B, and/or Ba, and/or Ce in the amount of 5-50%, trivalent neodymium Nd in the amount of l-7% and trivalent ytterbium Yb in the amount of 0.1-5.0%. The glass is characterized by high specific energy stored by Y'b in the active element at a section of stimulated emission of at least 2.5'10- cm.

The present invention relates to glass compositions and, more particularly, to glass for laser use in quantum electronics and intended for the generation and amplification of stimulated emission, namely for the generation and amplification of high-power monopulses and a duration less than 10- sec. at N=1060 nm.

At present there are known phosphate base glass materials for laser use and having the following composition in weight percent:

La O 14 B210 23 P205 so Nd o 3.0

Li O 240 Na O 2-40 P205 30-90 A1203 0-5 "ice This composition is activated with Nd o and Yb O taken together in the amount up to 15 percent by weight.

In this composition the working laser ion is Yb taken in the trivalent state, while ion Nd also taken in the trivalent state is used as a sensitizer, i.e. it consumes the energy of light pumping and transmitting it to Yb The disadvantage of these glass compositions consists in a low section of radiation of stimulated emission of Yb at N=1060 nm. equal to 2-10- cm.

In this case light fluxes up to 10 photon/cm. or 200 joule/cm. are necessary for full recovery of the energy stored by Yb.

Such fluxes are beyond the surface light resistance of the glass compositions during the monopulse operation of the laser. I

Another disadvantage of the above glass compositions consists in that in the glass serving as an active element of the laser there appears a nonhomogeneous change in the refraction index (depending on the temperature gradient of the glass) equivalent to an optical lens, the sign and value of which depend on the energy of light pumping and the shape of the illumination unit.

Moreover, known in the art are silicate and borate base glasses in which oxides of the majority of metals of the Periodic Table are used as modifiers.

For the purpose of employing the known silicate and borate base glasses in monopulse laser devices, attempts have been made to activate them with neodymium Nd.

Owing to the fact that Nd features high-intensity stimulated emission (higher than l.5'10'- cm. these attempts have given no positive results, since, as men tioned above, in this case, the laser devices must be considerably complex.

Also known in the art are silicate and borate base glasses activated with Nd and Yb in the trivalent state.

The common disadvantage of both borate and silicate glasses consists in that Yb in them has an extremely low section of stimulated emission at N=1060 nm. equal to 1.0-1.5 40- cm.

In addition, silicate base glasses are disadvantageous in that in order for the energy to be completely taken off from Nd, a high concentration of Yb is to be taken, which results in a high threshold energy of the laser.

Since borate base glasses are characterized by extremely low quantum yield and short life in excited condition (78-l0- sec.), the energy characteristics of the laser devices are drastically deteriorated and this is also a significant disadvantage of borate base glasses.

An object of the present invention is to provide a glass composition which eliminates the above-mentioned disadvantages.

Another object of the invention is to provide high specific values of energy stored by Yb in active elements.

Still another object of the invention is to obtain an efficiency factor of lasers operating under monopulse conditions close to that obtained under conditions of free generation.

Yet another object of the invention is to provide conditions of internal Q-modulation resulting in generation of separated giant laser pulses without using external modulators.

A specific object of the invention is to provide such a composition of glass that provides a section of stimulated emission of Yb at 7r=1060 nm. of 2.5-5 -10- cmfl, a life of Yb of 1.0-1.8-10- sec., a working concentration of Yb up to 3-10 cm.- a low thermo-optic constant at adequate technological peculiarities.

These and other objects are attained by a glass composition containing metaphopshates of the elements Li and/ or Na, and/or K, and/or Zn, and/or Cd, and/or Ba, and/or Pb as well as trivalent neodymium and ytterbium, and according to the invention, the glass composition also contains metaphosphates of the elements Mg and/or Ca, and/or Sr and phosphates of elements Al and/or Zr, and/or B, and/ or Ce, in which case all the components are taken in the following quantities, in percent by weight: 40-90% of the metaphosphates of elements Li and/or Na, and/or K, and/or Mg, and/ or Ca, and/or Sr, and/or Cd, and/or Ba, and/or Pb; 5-50% of the phosphates of elements Al and/ or Zr, and/or B, and/ or Ce; and 1-7% of Nd; and 0.3-5.0% of Yb Ionic uranyl, U is preferably added as a brightening absorber in the amount of 0.1 to 1.0% by weight.

The phosphates of the elements Al, B, Ce, Zr may be replaced with the oxides A1 0 B 0 CeO ZrO and also Nb O which replacement might be important for reducing the crystallizing capacity of the glasses, decreasing the temperature expansion coefiicient and increasing the chemical resistance of the glass.

One particular composition of the glass, in percent by weight, is:

Ba(Po 40-70 Pb(PO 25 Al(P0 8-20 KPo 1-10 Nd 1 s Yb 1-3 Another particular composition of the glass, in percent by weight, is:

Pb(PO 60-80 Nb O 1-10 KPO 5-25 Nd 1-5 Y'b 1-3 Another particular composition of the glass, in percent by weight, is:

KPo 50 s0 Mg(PO -30 B203 8-15 ceo 0.1-2 'Nd 2-s Yb 1-4 UO22+ 01-10 A further particular composition of the glass, in percent by weight, is:

NaPO 50-80 B 0 8-15 Ce0 0.2-2.0 Nd 2-5 Another particular composition of the glass, in percent by weight, is:

Ba(PO 60-80 Al(PO 10-30 Bro, 1-10 ceo 0.5-3.0 Nd 1-5 Yb 1-3 Yb, while for a large radius of modifiers in the glass (for example Cd Pb Ba they increase the section of stimulated emission of Yb The addition of uranyl U0 makes it possible to obtain the conditions of internal Q-modulation of the laser. During the excitation of light pumping, an additional absorption with a section at a wavelength Aa1066 nm. of 3-5 10' cm. appears in the uranyl, which can be brightened by an intensive light flux.

In this case, the section of the brightening is 2-10 cm. and this is much higher than the section of stimulated emission of Yb at a Wavelength X51060 nm. so that the conditions of brightening are fulfilled.

The proposed composition includes glasses with zero, low positive and low negative thermo-optical coefficients and this is extremely important for development of highpower laser devices.

The proposed glass of the invention is produced by a conventional method including the following operations: preparation of a charge; smelting of the charge; melting of the glass mass, the latter stage including an operation of brightening of the glass with subsequent roasting of the obtained glass mass.

In this case the fusing temperature of the charge is 950- 1300 C., while the roasting temperature of the glass mass is 300-500 C.

The charge is prepared by mixing the following components: metaphosphates or primary orthophosphates of Li, Na, K, Mg, Sr, Ba, Zn, Cd, Pb (40-90%) taken separately or in combination; phosphates of Al, Zn, B and Ce (5-50%) also taken separately or in combination depending on the composition and quality of the glass.

Trivalent ions of neodymium and ytterbium may be added into the charge in the form of oxides, fluorides, phosphates, nitrates and other compounds providing for neutral or oxidizing conditions to avoid the transition of Yb into Yb The ion U0 is added in the form of uranyl-nitrates, uranyl-chlorides and uranyl-fluorides.

Instead of metaphosphates, the starting components of the charge may be composed of oxides or oxygen compounds of Li, Na, K, Mg, Sr, Ba, Zn, Cd, Pb, and P 0 taken in such a proportion that Me OaP O and MeO:P O are equal to unity.

In this case the metaphosphates are formed in the process of melting the charge.

Given below are compositions of glasses and descriptions of processes of preparation of a charge for these glasses.

EXAMPLE 1 The charge is taken in parts by weight:

The glass comprises the following components, in percent by Weight:

Ba(PO3)2 Pb(PO 16.0 AI(PO 20.0 KPo 9.0 C602 Nd 2.83 Yb 1.17

The obtained glass has the following characteristics: coefiicient of thermal expansion 0c=135.10 1/deg.; a microhardnes of 300 kg./mm. the quantum efficiency of transmission Nd Yb is higher than 0.07; the life of 5 the level of Yb is 14-10" sec.; the section of stimulated emission of Yb at t=l060 nm. is equal approximately to 3 -10- cm. the maximum inversion at electric energy of pumping of '80 joule/cm. is 1.5- 10+ 1/ cm EXAMPLE 2 The charge contains the following components,'in per cent by weight:

Ba(H P 65.0 Pb(H PO 24.2 Al(PO 100.0 KH2PO4 4.6 Nd O 5.6 Yb O 2.3

The obtained glass contains the following components, in percent by weight:

Ba(PO Pb ('PO 22.0 A1(P0, 10.0 KPO 4.0 Nd 4.0 Yb 2.0

The glass obtained is characterized by the following parameters: coeflicient of thermal expansion a= 125{10 l/degree; the microhardness is 350 kg./mm. the life of the level of Yb is 1.3 -1( sec.; the section of stimulated emission Yb at 1060 nm. is -4-10- cm); the quantum efficiency of transmission Nd Yb is higher than 0.9; the maximum inversion at an electric pumping of 80 joule/ cm. is 2l0+ 1/cm.

EXAMPLE 3 The charge contains the following components, in parts by weight:

Pb(PO 67.0 KH2PO4 7.5 Nb O 7.5 Nd o 4.0 [0 0 1.33 a z s 0.17

Glass is produced containing the following components, in percent by weight:

s)2 67.0 KPO 20.0 Nb O 7.5 Nd3+ 3.43 Yb3+ 1.17 U0 0.1

The charge contains the following components, in parts by weight:

1 1500, 80.0 KPo 5.0 Nb205 9.0 Nd Ce 5.3 YbCe 1.7 UO (NO '6H 0 0.1856

Glass is obtained, containing the following components, in percent by weight:

Pb(PO 80.0

6 KPo 5.0 Nb O 9.0 Nd 3.8 Yb 1.5 Uo, 0.1

"The obtained glass is characterized by the following parameters: thermal expansion coefiicient a=-10 l/degree; the microhardness is 300 kg./mm. The laser characteristics of this glass are equivalent to those of the glass obtained by Example 3.

EXAMPLE 5 The charge contains the following components, in parts by weight:

KPo 55.0 11 190 17.75 Mg(H PO '4H O Ce0 0.1 Nd 0 3.5 Yb,0 1.3 UO2(NO3)2'6H2O 0.1856

The obtained glass contains the following components, in percent by weight:

KPo 55.0 B203 10.0 Mg(PO 30.0 cs0, 0.1 Nd 3.0 Yb 1.14 U02 0.1

The glass has the following characteristics: thermal expansion coefiicient a=-10- l/degree, the microhardne'ss is 400 kg./mm. the thermo-optical coefficient is 10" l/degree, the section of stimulated emission of Yb3+ at x=1060 3- 10* cm. the other laser parameters being close to those for the glass of Example 3.

EXAMPLE 6 The charge has the following composition, parts by weight:

KH2P04 69.2 H3303 24.85 Mg(H PO -4H O 31-9 CeO 0.1 Na o 4.15 5,0, 1.6 U02 0.15

The obtained glass contains the following components, in percent by weight:

KPo 60.0 B 0 14.0

C002 Nd 3.56 Yb O 1.4 U0 0.15

The glass features the following characteristics: thermal expansion .coefficient a='10 1/degree,.the micro-hardness is 350 kg./mm. the laser characteristics of the glass being close to those of the glass of Example 5.

EXAMPLE 7 The charge contains, in parts by weight:

NaPO 60.0 B 0 10.0 Mg(H PO -4H O CeO 0.2 Nil- 0 5 .0 Yb O 2.0

' 7 The obtained glass contains the following components, in percent by weight:

NaPO B 10.0 Mg(PO 22.8 CeO 0.2 Nd 4.29 Yb 1.76

EXAMPLE 8 The charge contains the following components, in parts by weight:

Ba(NO 63.8 1, 3.47 B1104 3.0 H PO, 77.5 Ce0 15.0 N0 0, 4.3 Yb O 1.2

The obtained glass contains the following components, in percent by weight:

3)2 72.0 3)3 18.0 BPO 3.0 Ce0 1.5 Nd 3.69 3+ 1.155

The obtained glass has the following characteristics: thermal expansion coefficient cz=110'10 I/degree, the microhardness is 450 kg./mm. the thermo-optical coefificient is +4.7, the quantum efiiciency of transmission Nd Yb the section of stimulated emission is 4.5 cm?, the maximum inverted population of Yb is 2-10 1/cm.

EXAMPLE 9 The charge contains the following components, in parts by weight:

ZII(HZPO4)Z Cd (H PO 21-1 0 49.3 LiHgP04 8.55 ZIIOQ 4.0 Nd O 3.5 Yb O 1.5

The obtained glass contains the following components, in percent by weight:

zn Po,) 45.0 capo. 39.0 LiPO 7.0 zro 4.0 Nd 3.0 Yb 1.32

EXAMPLE 10 The charge, in parts by weight:

zn H,Po, ,-2H,o' 26.5 Cd(H2PO4)22H20 LiH PO 2.44 zro, 2.0 Nd O 3.5 v1. 0, 1.5

The obtained glass contains the following components, in percent by weight:

ZII(PO 20.0 cd Po 71.0 LiPo 2.0 ZIOz 2.0 Nd 3.0

The obtained glass has the following characteristics: thermal expansion coefficient a=60-10- l/degree, the microhardness is 300 kg./mm. the section of stimulated emission of Yb at ).=1060 nm. is 3.5 -10 cm. the other laser parameters being close to those given in Example 9.

EXAMPLE 11 The charge contains the following components, in parts by weight:

The obtained glass has the following characteristics: thermal expansion coefircient a=l00'10 I/degree, the microhardness is 380 kg./mm. the quantum efi'lciency of transmission Nd Yb is at least 0.7, the section of stimulated emission at A=1060 nm. is 3.2-10- cm. the maximum inverted population of Yb under the pumping conditions given in the above example is 1.5-10+ l/cmfi.

EXAMPLE 12 The charge contains the following components, in parts by weight:

C3.(H3Po )2'H 0 SI'(H2PO4)3 Al(PO i 10.0 Nd O 3.5 Yb203 1.5

The obtained glass contains the following components,

in percent by weight:

a)2 40.0 SI'(PO3)2 a)a 10.0 Nd 3.0 Yb 1.32

The obtained glass has the following characteristics: the section of stimulated emission of Y1) at 7.21060 nm. is 2.7-lO- cmF. The other laser parameters are close to those given in Example 11.

We claim:

1. A glass for laser use comprising the following components, in percent by weight: 40-90% of metaphosphates selected from the group consisting of Li, Na, K, Zn, Cd, Ba, Pb, Mg, Ca, and Sr; 5-50% of phosphates of elements selected from the group consisting of Al, Zr, B, and Ce; 1-7% of trivalent neodymium Nd; and 0.3-5 of trivalent ytterbium Yb, said glass having a thermal expansion coefficient in the range of 5O-160 10-" l/degree, a microhardness in the range of 300-450 kg./mm. a

9 quantum efiiciency of transmission of Nd Yb higher than 0.7, the section of stimulated emission of ytterbium at 1:1060 nm. being equal to about 2.5-5 10 cmF, and a maximum inversion at electric energy of pumping of 80 joules/cm. is 1.5 to 2 10 1/cm.

2. Glass as claimed in claim 1, containing also uranyl UO in the amount of 0.1-1.0% by Weight.

3. Glass as claimed in claim 1 containing at least one oxide selected from the group consisting of A1 B 0 020 and N'b O in an amount of 05-20% by weight.

4. Glass as claimed in claim 1, containing the following components, in percent by weight:

BE1(PO3)2 .L Pb(PO -2s KPO, 1-10 Al(PO 8-20 Nd l-5 Yb 1-3 5. Glass as claimed in claims 1 and 3, containing the following components, in percent by weight:

Pb(PO 60-80 KPo 5-25 Nb o 1-10 N 1-5 Yb 1-3 6. Glass as claimed in claim 2, containing the following components, in percent by weight:

10 7. Glass as claimed in claim 3 containing the following components, in percent by Weight:

NaPO 50-80 5 B 0 ..i -1 8-15 C60 0.2-2.0 Nd ...L 2-5 Yb 1-4 8. Glass as claimed in claim 3, containing the following 10 components, in percent by weight:

Ba(PO 60-80 Al(PO 10-30 BPo 1 10 CeO 0.5-3.0 Nd 1-5 Yb 1-3 References Cited UNITED STATES PATENTS 3,580,859 5/1971 Buzhinsky et al. 252301.4 P 3,068,108 12/1962 Geficken 10647 Q 3,281,253 10/1966 Weidel 10653 3,328,181 6/1967 Weidel 10647 Q 3,455,707 7/1969 Jahn 1O647 Q 3,516,939 6/1970 Yohata et al 10647 R 3,549,554 12/1970 Huayama 106-47 R 3,250,721 5/1966 De Paolis et a1 106-47 R WINSTON A. DOUGLAS, Primary Examiner M. L. BELL, Assistant Examiner US. (:1. xx.

10647 Q; 2s2 301.4 P 

1. A GLASS FOR LASER USE COMPRISING THE FOLLOWING COMPONENTS, IN PRESENT BY WEIGHT-40-90% OF METAPHOSPHATES SELECTED FROM THE GROUP CONSISTING OF LI, NA, K, ZN, CD, BA, PB, MG, CA, AND SR, 5-50% OF PHOSPHATES OF ELEMENTS SELECTED FROM THE GROUP CONSISTING OF AL, ZR, B, AND CE, 1-7% OF TRIVALENT NEODYMIUM ND3+, AND 0.3-5% OF TRIVALENT YTTERBIUM UB3+, SAID GLASS HAVING A THERMAL EXPANSION COEFFICIENT IN THE RANGE OF 50-160X10**-7 1/DEGREE, A MICROHARDNESS IN THE RANGE OF 300-450 KG./MM,2,A QUANTUM EFFICIENCY OF TRANSMISSION OF ND3+>YB3+HIGHER THAN 0.7, THE SECTION OF STIMULATED EMISSION OF YTTERBIUM AT X=1060 NM. BEING EQUAL TO ABOUT 2.5-5X10**-21 CM.2, AND A MAXIMUM INVERSION AT ELECTRIC ENERGY OF PUMPING OF 80 JOULES/CM.3 IS 1.5 TO 2X10**19 1/CM.2. 